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Near‐field dosimetry of I 125 sources for interstitial brachytherapy implants measured using thermoluminescent sheets
Author(s) -
Iwata Kazuro,
Yue Ning J.,
Nath Ravinder
Publication year - 2004
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1820012
Subject(s) - thermoluminescence , anisotropy , dosimetry , brachytherapy , materials science , thermoluminescent dosimetry , thermoluminescent dosimeter , nuclear medicine , optics , physics , luminescence , dosimeter , medicine , optoelectronics , radiation therapy
The dosimetric characteristics were measured for two types of I125 low‐energy photon‐emitting sources by using a wide and highly sensitive thermoluminescent (TL) sheet film, which was developed for two‐dimensional dose distribution measurements. The TL film is made of Teflon homogeneously mixed with small powders of thermoluminescence ( Ba S O 4 : Eu doped). Various dosimetric parameters (i.e., radial dose function, 2D and 1D anisotropy functions) of model 6711 and 6702 I125 sources were obtained at various distances from the source surfaces to 15 mm . These parameters obtained with TL sheet were compared with the data recommended in the updated AAPM TG‐43 report. The radial dose functions measured with TL sheet are in agreement with those established data of model 6711 I125 seed and model 6702 I125 seed at most of the distances within 5% and 7%, respectively. All the measured anisotropy functions showed symmetry about the longitudinal source axis. The anisotropy of dose distributions was clearly present in the immediate vicinity of the source edges. The measured 2D anisotropy function values at 1 cm are in reasonably good agreement with the recommended values. The differences at two points in the 1D anisotropy functions measured with TL sheet and the established data at 1 cm from source center were 0.7% and 1.9% for model 6711 and 6702 I125 sources, respectively; the differences at 0.5 cm were 1.5% and 1.7% for model 6711 and 6702 I125 sources, respectively. The relative dosimetric characteristics in the vicinity of actual interstitial brachytherapy sources containing I125 have been experimentally determined by using the TL sheet as a 2D dosimeter.